1. Load https://bug507563.bugzilla.mozilla.org/attachment.cgi?id=391797 2. Drag the scrollbar thumb around at random, picking it up and letting it go several times. Result: ###!!! ASSERTION: curPos.x not a multiple of device pixels: 'curPosDevPx.x*appUnitsPerDevPixel == curPos.x', file /Users/jruderman/central/layout/generic/nsGfxScrollFrame.cpp, line 1763 This assertion was added in rev 4ccff5df452c: "Bug 526394. Part 31: Move scroll implementation into nsGfxScrollFrame."
Created attachment 421384 [details] another testcase This testcase triggers the assertion on load, but only at certain window sizes :/
Can't seem to reproduce on Linux. Maybe Mac only.
Zooming in attachment 266235 [details] also triggers this assertion. And bug 561676 is an orange that might be related to this assertion
Bug 681192 Part 1 removed the assertion: https://hg.mozilla.org/mozilla-central/rev/9e1f8d125acc